[1S,1(2S,5S,2'R,5'S,5'(1R)),2S,3R,4R]-benzoic acid 1-[2,5'-dimethyl-5'-(1-t-butyldimethylsilyloxy-ethyl)-octahydro-[2,2']bifuranyl-5-ylmethyl]-2,4-dimethyl-3-triisopropylsilyloxy-5-trityloxy-pentyl ester